Liquid fuel discharge nozzles



March 17, 1959 s. c. WATKINS 2,878,065

LIQUID FUEL DISCHARGE NOZZLES Filed July 8, 1957 y z t f e P x 1 l\ T 47 d f, h 1 K 3L 1 IV 0 a X U flzcezzizr 6. CHa/ikuzw Unite Sates LIQUIDFUEL DISCHARGE NOZZLES Sidney C. Watkins, Burnley, England, assignor toJoseph Lucas (lnclusnies) Limited, Birmingham, England This inventionrelates to liquid fuel discharge nozzles of the swirl type for supplyingfuel in a nebulised condition to a combustion chamber.

In a nozzle of conventional form the liquid is supplied tangentially toa conical swirl chamber having a small discharge orifice at its apex.While passing through the swirl chamber a rapid rotary or eddy motion isimparted to the fuel, so causing it to issue from the nozzle in the formof a thin hollow conical film which quickly disintegrates into thecondition of a fine mist. To obtain satisfactory nebulisation it isnecessary to supply the fuel at a sufiiciently high rate, and in thiscondition an axial air core is set up in the liquid in the swirlchamber. When the liquid is supplied at a low rate at which no air coreis formed, the issuing jet breaks up into relatively coarse drops, andthe resulting fuel-air mixture is unsatisfactory where a high rate ofcombustion is required.

For some purposes it is necessary to be able to vary the rate of fuelsupply over a wide range, and for such a purpose a swirl nozzle ofconventional form is unsatisfactory in that it does not effect propernebulisation of the fuel when the latter is supplied at a low rate.

The object of the present invention is to provide a nozzle of theaforesaid type in an improved form which enables satisfactorynebulisation of the fuel to be obtained over a wide range of rate ofsupply of the fuel.

A nozzle in accordance with the invention includes a swirl chamberhaving a discharge orifice at its apex and an axial orifice in its base,a cavity into which fuel can flow from the swirl chamber when no aircore exists in the said chamber, and an air duct in communication withthe said cavity and terminating in a discharge orifice coaxial with thedischarge orifice of the swirl chamber, the arrangement being such thatat a low rate of fuel supply air-nebulisation of the fuel is effected inthe air duct, and at a high rate of fuel supply, swirl-nebulisation iseffected by discharge from the swirl chamber.

In the accompanying drawing, Figure l is a sectional side elevation of anozzle embodying the invention, and Figure 2 is an end view of one ofthe components of the nozzle.

Referring to the drawings, the body part a has formed in it a passage bfor conveyance of the liquid fuel supplied by a pump, and a passage cfor conveyance of air supplied by a blower or other convenient source.At the front end of the body part is placed a hollow nipple d. The rearend of the nipple is of hollow cylindrical form and in it are containedtwo inserts e, f. The forward end of the nipple is of conical shape andon its outer periphery are formed helical or like air grooves g (Fig ure2) adapted to impart a Swirling motion to the air flowing therein. Alsowithin the forward end of the nipple is formed a conical chamber hforming part of atent 2 the swirl chamber and terminating in an axialdischarge orifice 1'.

At the centre of the front face of the insert e is formed a cylindricalrecess 1' of the same diameter as the larger end of the chamber h andforming the inner end of the swirl chamber. This recess communicates byway of a central hole k with a shallow recess m in the rear face of theinsert e. In this insert are formed three equispaced ports 11 whichcommunicate with the swirl chamber through tangential grooves 0 formedin the front face of the insert. Also in this insert are formed threeother equi-spaced ports p which communiacte with the said recess inthrough grooves q formed in the rear face of the insert. The ports n arearranged between the ports p as shown in Figure 2. Further the ports pcommunicate with the grooves g through holes r. Preferably each grooveis so shaped that at a position adjacent to the associated hole it is ofless width than at its ends in order to form a venturi threat at thatposition.

In the insert are formed three equi-spaced ports s (of which only oneappears in Figure 1) through which the fuel is conveyed from the passageb to the ports n in the insert 2, and air is conveyed from the passage 0to an annular space 2 surrounding the nipple through a pas sage u.

'Over the front end of the body a is placed a sleeve v which is shapedinternally to form the outer boundary of the annular air passage t andof the grooves g, and in the front end of this sleeve is formed acentral orifice w.

The various components above described are secured in position on thebody part by an outer sleeve x having a screw thread connection with thebody part. Preferably the sleeve x is shaped to form with the sleeve 1 anarrow annular air space y into which an air stream can flow throughports z from the surrounding air in the combustion chamber, this passagebeing adapted at its outlet end to deflect the air across the front ofthe sleeve v for minimising the formation of carbon deposits on thefront of the nozzle, this being a device which is already known andforms no essential part of the present invention.

The arrangement is such that with a low rate of fuel supply at which noair core is formed in the swirl chamber, the fuel passes from the recess1' through the hole k and thence through the recess m, grooves q, portsp and holes r to the air grooves g. Here the fuel is nebulised by theair stream flowing along the said grooves from the annular space t andthe mixture of air and fuel is discharged through the orifice w. Whenthe fuel is supplied at a sufliciently high rate to cause an air core tobe set up in the swirl chamber, the air core confines the fuel to thesaid chamber. No fuel then flows through the hole k and the nebulisationof the fuel then depends on the swirl of the fuel issuing through theorifice i.

Having thus described my invention What I claim as new and desire tosecure by Letters Patent is:

A liquid fuel discharge nozzle comprising in combination a body parthaving therein a fuel supply passage and an air supply passage, meansdefining at one end of said body part a conical swirl chamber having itsapex directed away from said body part and provided with a dischargeorifice, and having an axial orifice in its base, and a cavity situatedbetween the base of said swirl chamber and the adjacent end of said bodypart, and communicating with said swirl chamber through said axialorifice, said swirl chamber having tangentially arranged fuel inlets, anair duct surrounding said means and having a discharge orifice coaxialwith and adjacent a 3 i e the discharge orifice in the apex of saidswirl chamber, core set up therein by the swirling fuel prevents fuelair swirling means in said duct, ports establishing comflow from saidswirl chamber to said cavity. municatlon between said fuel supplypassage and the fuel References Cited in the file of this Patent inletsof said swirl chamber, and additional ports establishing communicationbetween said cavity and said air 5 UNITED STATES PATENTS duct, so thatat a low rate of fuel supply to said swirl 1,474,603 Morse Nov. 20, 1923chamber fuel flows therefrom to said cavity and thence 2,303,104 AbbeyNov. 24, 1924 through said additional ports to said air duct, whereas at2,701,164 Plln has Feb. 1, 1955 a high rate of fuel supply to said'swir'l chamber the air 2,762,657 W n S p 9

